It is often desired to generate a multiplicity of radio signals with similar modulation formats to be combined and transmitted from a single antenna. For example, the hub station (HS) of a star configured network may transmit signals on a number of different frequency channels. Each of these channels may have a multiplicity of signals that employ code division multiple access (CDMA). As an illustration, the 18-95 CDMA cellular standard forward link calls for a number of 1.25 MHz channels each containing as many as 64 orthogonal CDMA signals.
Further, the signals may be transmitted on multiple antennas to provide spatial diversity. In addition, in a satellite system, the antenna system may be duplicated so that more than one satellite can be addressed simultaneously.
The straight forward approach of generating individual modulated RF signals and combining them may result in very cumbersome hardware due to the large number of links.